Rewrite Meter_humanUnit() to accept floating point value

Since Meter_humanUnit() is often called with floating point values in
Meter objects, rewrite the function to let it process `double` type
natively, and save floating point to integer casts.

The rewritten function:
* Allows higher orders of magnitude including 'R' and 'Q', and
  addresses infinity. (The previous version has a maximum value of
  (2^64 - 1) representing 16 ZiB.)
* Rounds values when they are in intervals (99.9, 100) and (9.99, 10),
  and displays them with correct precision (number of fraction digits).
* Produces assertion error on negative and NaN values (undefined
  behavior).

Signed-off-by: Kang-Che Sung <explorer09@gmail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/XUtils.h b/XUtils.h
index cfb375cc..afe22112 100644
--- a/XUtils.h
+++ b/XUtils.h
@@ -111,4 +111,7 @@ int compareRealNumbers(double a, double b);
    nonnegative. */
 double sumPositiveValues(const double* array, size_t count);
 
+/* IEC unit prefixes */
+static const char unitPrefixes[] = { 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y', 'R', 'Q' };
+
 #endif